diff --git a/CMakeLists.txt b/CMakeLists.txt
index ef7fc5a..203e57d 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -56,6 +56,24 @@ if (execution_results MATCHES FAILED_TO_RUN)
     )
 endif()
 
+## 2. Find Flex and Bison
+
+include(macosx_homebrew)
+
+if (CMAKE_HOST_APPLE)
+  find_package_prefer_brew(BISON REQUIRED)
+  find_package_prefer_brew(FLEX 2.5 REQUIRED)
+else()
+  find_package(BISON REQUIRED)
+  find_package(FLEX 2.5 REQUIRED)
+endif()
+
+if (BISON_VERSION VERSION_LESS 2.5)
+    message(FATAL_ERROR "At least Bison 2.5 is required.")
+elseif(BISON_VERSION VERSION_LESS 3.0)
+    message("== Bison 2.5 was found. You have to apply cmake/bison2.patch...")
+endif()
+
 ## 2. Build Monicelli
 
 include(package)
diff --git a/cmake/macosx_homebrew.cmake b/cmake/macosx_homebrew.cmake
new file mode 100644
index 0000000..947d335
--- /dev/null
+++ b/cmake/macosx_homebrew.cmake
@@ -0,0 +1,75 @@
+#
+# Monicelli: an esoteric language compiler
+# 
+# Copyright (C) 2014 Stefano Sanfilippo
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+
+# The following macro has been adapted from
+# https://gist.github.com/steakknife/c36c99b51703fc6f6c1b
+
+# If is running under Mac OS X and the Homebrew package manager is installed,
+# then Homebrew-specific directories for the given package are automatically
+# added to the appropriate CMake search paths.
+
+macro(find_package_prefer_brew _package)
+  unset(_brew_path)
+  unset(_brew_pkg_lower)
+  unset(_has_brew)
+  find_program(_has_brew NAMES brew DOC "path to Homebrew executable")
+  if(_has_brew)
+    string(TOLOWER ${_package} _brew_pkg_lower)
+    execute_process(COMMAND brew --prefix ${_brew_pkg_lower} ERROR_QUIET
+        OUTPUT_STRIP_TRAILING_WHITESPACE OUTPUT_VARIABLE _brew_path)
+    if(EXISTS ${_brew_path})
+      set(_brew_cmake_module_path ${CMAKE_MODULE_PATH})
+      set(_brew_cmake_program_path ${CMAKE_PROGRAM_PATH})
+      set(_brew_cmake_include_path ${CMAKE_INCLUDE_PATH})
+      set(_brew_cmake_library_path ${CMAKE_LIBRARY_PATH})
+
+      if(NOT CMAKE_MODULE_PATH)
+        list(INSERT CMAKE_MODULE_PATH 0 "${_brew_path}")
+      endif()
+
+      if(NOT CMAKE_PROGRAM_PATH AND EXISTS "${_brew_path}/bin")
+        list(INSERT CMAKE_PROGRAM_PATH 0 "${_brew_path}/bin")
+      endif()
+
+      if(NOT CMAKE_INCLUDE_PATH AND EXISTS "${_brew_path}/include")
+        list(INSERT CMAKE_INCLUDE_PATH 0 "${_brew_path}/include")
+      endif()
+
+      if(NOT CMAKE_LIBRARY_PATH AND EXISTS "${_brew_path}/lib")
+        list(INSERT CMAKE_LIBRARY_PATH 0 "${_brew_path}/lib")
+      endif()
+
+      find_package(${_package} ${ARGN})
+
+      set(CMAKE_MODULE_PATH ${_brew_cmake_module_path})
+      set(CMAKE_PROGRAM_PATH ${_brew_cmake_program_path})
+      set(CMAKE_INCLUDE_PATH ${_brew_cmake_include_path})
+      set(CMAKE_LIBRARY_PATH ${_brew_cmake_library_path})
+
+      unset(_brew_cmake_module_path)
+      unset(_brew_cmake_program_path)
+      unset(_brew_cmake_include_path)
+      unset(_brew_cmake_library_path)
+    else()
+      find_package(${_package} ${ARGN})
+    endif()
+  else()
+    find_package(${_package} ${ARGN})
+  endif()
+endmacro(find_package_prefer_brew)